The Relationships Between Soil Health, Production, and Management Decisions Through Farmers’ Eyes: A Case Study of Tennessee Large-Scale Vegetable Farms

Abstract

Understanding farmers’ perceptions of soil health is valuable for developing strategies to increase the adoption of conservation practices. A combination of soils with poor soil fertility, low levels of soil organic matter, and the use of production practices that, although necessary for vegetable production, could negatively impact soil health makes the exploration of how large-scale vegetable producers in Tennessee perceive soil health and manage soils interesting. Using information from semi-structured interviews with operators of three Tennessee large-scale vegetable farms, we explored farmers’ perceptions of soil health and how those perceptions connect with adoption decisions. Our results suggest that farmers’ perceptions of soil health reflect a broad perspective that includes crop productivity and disease pressure. Profitability exerted a stronger influence on farmers’ decision-making than soil health. Nonetheless, farmers recognized that there is an association between soil health and profitability. The farmers included in this study found value in the information provided by soil health tests to confirm the benefits of soil management practices. The results presented in this study will contribute to the design of future studies aiming to investigate the relationship between farmer perceptions of soil health and the adoption of best soil management practices among large-scale vegetable growers.

1. Introduction

Soil health has been at the center of recent discussions on climate mitigation and adaptation strategies [1,2,3]. Therefore, some US policymakers and other stakeholders interested in improving the resiliency of agricultural systems have tried to develop strategies to increase farmers’ awareness and adoption of best soil management strategies. Previous studies suggested that some of those efforts have failed because of the lack of understanding of the farmers’ knowledge and perceptions of soil health [2,4]. Farmers’ conceptualization of soil health informs their decision-making process, and sustainable soil management relies on farmers’ behavior [3,5]. Therefore, it is important to improve the understanding of farmers’ perceptions and knowledge associated with soil health to inform strategies aiming to increase their adoption of soil management practices that could improve soil health [1,3,6].

The Natural Resources Conservation Service (NRCS) defines soil health as the continuous ability of soil to function as a living ecosystem that can sustain plants, animals, and human beings [7]. Other studies expand on this basic concept and refer to soil health as the ability of soil to improve ecosystem resiliency and promote plant, animal, and human health [1,2,4,8,9]. A common framework for the assessment of soil health includes characteristics of soil health that are classified into three main categories: physical characteristics, biological characteristics, and chemical characteristics [1,2,4,10]. Farmer perceptions of soil health could vary based on the location and type of crop grown because the climate, geology, topography, land use, and management history could impact soil characteristics [1]. Therefore, farmers’ decision-making process related to soil health could also vary depending on the crops grown and the farm’s location [6,9,11].

As suggested by previous studies, the adoption of environmentally sustainable production practices that could improve soil health is correlated with farmer and farm business characteristics [12,13,14]. Soil health, specifically farmers’ perceptions of soil health, is an additional component that could impact this decision-making process and one that has not been evaluated to such an extent, specifically in the context of decision-making processes related to conservation agriculture. Previous studies have explored farmers’ perceptions of soil health and how they incorporate this information into their decision-making processes [5,6,11,15]. Only a few studies have evaluated US farmers’ perceptions of soil health, specifically row crop farmers [2,3,9,10,16]. There is only one study [17], as far as we know, evaluating US vegetable farmers’ perceptions of soil health. In [17], the authors investigated farmers’ knowledge of soil health and the management practices they use to improve soil health in the context of organic agriculture in Yolo County, California. This study contributes to the emerging social science literature on farmers’ perceptions of soil health, which has focused mainly on row crop farmers.

There are unique production practices in large-scale vegetable production that could impact how farmers view soil health and how they make decisions about the adoption of practices that could improve soil health. Vegetable production on a large scale entails practices such as tillage, laying plastic mulch, and multiple machinery passes for field preparation that, while needed to maintain yield and crop quality, could negatively impact soil health [18,19]. These practices are less likely to be used by small- and medium-scale farms. For example, small-scale operations might use alternative mulch options, such as hay or other organic mulches [20].

The southeast Appalachian region, where states contributing significantly to US vegetable production are located, has highly weathered soils (e.g., ultisols) characterized by lower pH, poor soil fertility, and low levels of soil organic matter. Previous studies indicated that in this region, no-tillage and cover crops are commonly used soil conservation practices among row crop farmers [21], but there are no data available about the use of soil conservation practices among vegetable farmers in this region.

Vegetable, melon, and potato farms located in the US southern states represent about 30 percent of all US vegetable farms and about 19 percent of the total vegetable, melon, and potato hectares harvested in the US [22]. Therefore, a better understanding of how soil health perceptions and knowledge impact farmers’ decision-making processes in the Southeast US could be of particular importance when promoting the adoption of soil management practices among vegetable farmers located in this region. Combining farmer knowledge with scientific knowledge could improve the understanding of the impacts and performance of conservation agriculture practices in terms of soil health [1,4,9].

In this study, we explore large-scale vegetable farmers’ perceptions of soil health and evaluate connections between their perceptions and decision-making processes at the farm level using information from semi-structured interviews conducted with the owners and/or managers of three large-scale vegetable farms in Tennessee. As far as we know, our study is the first one to attempt to capture information about perceptions of soil health and the use of soil health management practices among large-scale vegetable farms. We focused on large-scale vegetable operations, as opposed to small- and medium-scale vegetable operations, because, as explained above, these operations tend to manage soil more intensively than small-scale and medium-scale operations. Therefore, decisions these farmers make regarding soil management practices will have important implications for soil health, given that it is expected that the more intense management of the soil could have negative impacts on soil health. We further investigate the relationships between farmers’ perceptions of soil health and soil health assessments and gauge their interest in this information. While the views of three large vegetable farmers in Tennessee will not represent the views of all Tennessee farmers or all vegetable farmers in the US Southeast region, we do believe the views of these farms might align with those of other large-scale vegetable farmers in the Southeast US and could serve as a foundation for future research.

2. Materials and Methods

2.1. Vegetable Farmers Included in the Study

The managers and/or owners of three large-scale tomato farms participated in semi-structured interviews. We targeted farmers growing the same crop (tomatoes) to avoid variability in perceptions related to the type of crops grown. We opted for farmers who owned or managed large-scale operations and who sold products through wholesale market outlets. These types of growers tend to manage soil more intensively than small-scale, diversified vegetable operations selling products through direct-to-consumer market outlets. These growers use production practices that small farms will not use, like soil fumigant application, multiple machinery passes for field preparation, mulch laying, and pesticide application. In these large-scale vegetable operations, cover crops (if the farmer is using cover crops) are incorporated using tillage four to six weeks in advance to prepare for tomato planting. Cover crops are crops that are grown after the end of the vegetable season and that are not intended for harvest. These crops are terminated and incorporated into the soil before planting vegetable crops. Cover crops increase soil organic matter, improve soil fertility, raise soil moisture capacity, prevent soil erosion, and reduce soil compaction (https://tiny.utk.edu/zDyeB, accessed on 20 December 2024) Pre-plant fertilizer is applied, then raised beds are formed, and plastic mulch and drip tape are laid with one pass of the tractor (Figure 1). Tomato transplants are planted into the plastic with a mechanical transplanter. Plants are fertigated weekly with N and K from planting through harvest.

We used a convenience sample approach based on our research team’s relationship with these farmers and their willingness to participate in this study [23]. The three farms included in this study represent about 6 percent of the total hectares of vegetable production in Tennessee. These farms are between 10 and 52 times the average vegetable farm size in Tennessee (i.e., 5 hectares) [22]. These farms will likely face challenges that are similar to those faced by other large vegetable farms in the Southeast US, such as disease pressure and other production challenges related to heat, humidity, and low levels of soil organic matter [24].

The fact that only three farmers participated in this study is explained by the time and effort necessary to build relationships prior to conducting interviews and collecting information through in-depth interviews [17]. The farmers’ willingness to participate in this research study is based on the trust relationship that has been built over many years between them and the research team.

There are also unique difficulties related to collecting data from large-scale vegetable operations. The owners or managers of large-scale vegetable farms selling products through wholesale markets are managing large product volumes, which implies more complex logistics and high time investment from production to marketing [25]. Therefore, coordinating farm visits with these kinds of farmers for research purposes is challenging. Completing interviews during two farm visits with three farmers took one and a half years, mainly because of difficulties related to finding times when they were available. We contacted farmers via phone multiple times to coordinate visits. Additionally, gathering information from large-scale operations with over $1 million in annual sales can be difficult. These operations might be more hesitant to share information with researchers, given that financially there is more at stake when sharing information with researchers.

Although a sample of three farms does not represent all large-scale vegetable farms in Tennessee, there are a few elements that make this information valuable. On the one hand, vegetable farms with more than 40 hectares in vegetable production only represent about 1.1% of all vegetable operations in Tennessee [22]. Specifically, there are only ten farms with vegetable production ranging between 40 and 99 hectares, three farms with vegetable production ranging between 100 and 199 hectares, and four farms with vegetable production ranging between 200 and 300 hectares. Therefore, the farms included in this study represent 18% of all Tennessee vegetable farms, with hectares in vegetable production ranging between 40 and 100.

Additionally, the views of owners or managers of large-scale Tennessee vegetable operations (i.e., more than 40 hectares) are missing in previous studies evaluating production practices that are likely to be used by these types of farms (e.g., polyethylene mulch) because the public contact lists used to conduct surveys are less likely to contain information on large-scale operations [26,27]. These contact lists tend to be biased towards small-scale operations selling produce through direct-to-consumer market outlets because these lists are related to programs that aim to assist Tennessee farmers in marketing (i.e., Pick Tennessee Products), specifically when trying to connect them with final consumers [26]. The owners or managers of large-scale operations are less likely to participate in these types of programs because they tend to sell their products through wholesale markets. When selling products through wholesale markets, the farmer connects to the buyers through intermediate channels, such as terminal markets or brokers [25].

2.2. Interview Protocol and Instrument

A multidisciplinary team, including a plant scientist, two economists, and a soil microbiologist, helped design the interview instrument and conducted the semi-structured interviews between January 2022 and March 2024. Prior to beginning this study, the interview instrument was approved by the University of Tennessee Institutional Review Board (IRB) (UTK IRB-22-07049-XM). The interdisciplinary nature of the approach we are taking in this study, where researchers who represent different disciplines (i.e., economics, plant science, soil microbiology) are involved in the development of interview instruments and conducting the interviews, helps address challenges identified when using farmer participatory research as a research methodology [28]. Specifically, the interdisciplinary approach taken in this study addresses challenges related to insufficient insight into systems’ complexity, differences in the reference framework, and methodological errors. We involved social scientists and biophysical scientists to try to understand the complexity of the system in which farmers understand and make decisions about soil health. We highlighted the fact that the immediate surroundings condition farmers’ perceptions of soil health and decisions related to soil health management.

We used a qualitative approach that relies on in-depth personal interviews to investigate farmers’ perceptions of soil health and how those are connected to their decisions associated with soil management practices. This approach allows us to access more in-depth knowledge, which seems more appropriate when investigating farmers’ perceptions of soil health [17].

The sections included in the interview protocol were (1) soil health; (2) land ownership; (3) field history and management strategies; (4) plastic mulch use; (5) stress events and field resiliency; (6) water use and water sources; and (7) labor use and labor challenges. The interview instrument is included in Appendix A. In this study, we will only present information from those sections related specifically to soil health perceptions and the relationship between these perceptions and the adoption of production management practices (i.e., Section 1, Section 2 and Section 3). We included questions about land ownership since previous studies have identified land tenure arrangements as an important dimension of soil health outcomes [29]. The questions included in the semi-structured interview instrument were exploratory in nature, which means we were letting the farmers contribute to the formulation of the questions by asking general questions that they could accommodate to the specific situation of their farms. For example, when exploring the concept of soil health, we did not provide a definition; rather, we let farmers define the health of farm fields based on their understanding of soil health.

We conducted two visits to each farm. During the first farm visit, we asked farmers to complete a form requesting information about their age and farming experience, their farm size in terms of hectares and gross sales, and the percentage of their household income from farming. The first interview lasted between 55 and 60 minutes and covered the seven sections in the aforementioned interview instrument. We then asked farmers to identify “good” and “not good” fields in terms of soil health based on their perceptions of soil health. In this case, we used a Farmer First approach, which recognizes farmers as experts and critical partners when conducting research [17]. We did not introduce a specific definition of soil health before conducting the interviews. We asked them to describe the soil characteristics they used to classify those two fields.

Similar to [11], we took soil samples of the fields identified by the farmer as “good” and “not good” based on their perceptions of soil health. Soil samples were collected using a 2 cm diameter stainless steel auger. Six 15 cm deep soil cores were taken from random locations within each field and composited. Soil samples were shipped to the Cornell Soil Health Lab for a Comprehensive Assessment of Soil Health (CASH) analysis in order to obtain measurements of wet aggregate stability, organic matter, active carbon, pH, modified Morgan extractable phosphorus (P), potassium (K), along with additional nutrients (Mg, Fe, Mn, Zn, Al, Ca, Cu, S, B) (https://soilhealthlab.cals.cornell.edu/testing-services/ accessed on 10 October 2024). In addition to the measured data, the CASH test provides ratings based on measured parameters calibrated against soils in the Northeastern US. A second visit was scheduled with the farmer to present the CASH test results. The second interview lasted between 30 and 50 minutes. Specifically, we let farmers ask questions about the results and asked them if the results deviated from what they were expecting from the fields they selected in terms of soil health.

2.3. Analysis

All interviews were audio-recorded, transcribed verbatim, and coded based on the seven interview sections. Content regarding sections one to three was used in this analysis. Emerging themes associated with farmers’ perceptions of soil health and management practices related to soil health were identified [2,30]. Coding was developed using the NVivo 14 software (QSR International, Burlington, MA, USA). Farmer perceptions of soil health were analyzed using the word frequency function in the NVivo 14 software. The criteria used for the word frequency analysis was stemmed words with a length of six letters to avoid linking words such as “and”. For all interview sections, we coded only farmers’ responses and did not include the actual questions and researcher comments to avoid including information related to researcher perceptions or thoughts. Given the exploratory nature of the methods used in this study, we do not intend to generalize results but rather to build the foundation for future research that could explore more in-depth the connection between large-scale vegetable farmers’ perceptions of soil health and their adoption of best soil management practices.

3. Results

3.1. Farmer and Farm Business Characteristics

The manager of Farm A and the owner of Farm B were in their 30s, while the owner of Farm C was in his 60s (Table 1). Years of experience in managing the farms were 10 to 12, 23, and 43 years for farms A, B, and C, respectively (Table 1). Levels of education varied greatly by participant, from high school to graduate degrees. Farm size in terms of hectares of vegetable production varied from 49 to 263 hectares. All of the interview participants indicated that about 75% of their taxable household income came from farming activities. Overall, all farms were large in terms of hectares and gross farm revenue (i.e., more than $1 million).

3.2. Perceptions of Soil Health

In order to gain insight into farmers’ views of soil health, we asked farmers, “What information and soil characteristics do you use to identify your “good” and “not good” fields regarding soil health?”. Farmer responses were visualized as word clouds to highlight frequently used terms (Figure 2). In Figure 1, differences in the size and color of the letters represent differences in the frequency in which a word was repeated relative to the total number of words counted. Words with bigger letters had a higher frequency of repetition compared to other words counted in the transcription. Words in orange and with larger letter sizes had the highest frequency of repetition relative to all words counted.

Farm A’s manager defined soil health in terms of productivity (e.g., “That field is productive”). Specifically, he believed that if a field is producing, then it is a “good” field in terms of soil health. In this farm, the manager perceived soilborne disease pressure as the limiting factor of productivity (i.e., “I believe that bad field does not produce because of the high level of Phytophthora.”). Farm B’s owner mentioned various characteristics that define the soil health of a field, such as organic matter, biological activity, and the percentage of exposed subsoil. The characteristics he used to distinguish a “good” field from a “not good” field were erosion, organic matter, and the percentage of exposed subsoil (i.e., “probably some of the better places I would think about like lower spots that have less erosion, high organic matter, less exposed subsoil.”). He mentioned micronutrients as a limiting factor (i.e., “I can control the water, I can control fertility, I can control everything, except for the micros (micronutrients)). Farm C’s owner defined soil health in terms of soil texture, the ability to work the field, and organic matter (i.e., “Soil Texture”, “The ability for us to work it”,” Organic matter in the soil”). Similar to the manager of Farm A, the owner of Farm C saw soilborne disease pressure as a limiting factor.

3.3. Soil Tests

We asked the farmers to tell us about their use of soil tests, in terms of the frequency of use, information gathered, and how soil test information was used to make production and management decisions. Farm A’s manager indicated that soil tests were conducted every two years to check pH levels and correct them when necessary (i.e., ”We only do soil tests to check pH”, “To assess whether pH needs to be corrected with lime”). After planting, they used tissue tests to adjust nutrient levels (i.e., “After we plant, we do not make soil tests because we take tissue samples.”). Farm B’s owner has his own pH meter that he uses to check pH levels in all his fields (i.e., “I do pH, I’ve got my own pH meter”). He indicated conducting soil tests every two to three years to check for micronutrients (“we are extremely high in P and K, so I’m not soil tested for P and K, I’m still testing for micros (micronutrients)”). He considers micronutrients to be the limiting factor; therefore, soil test information is used to address micronutrient issues through a fertility plan. Farm C’s owner reported conducting soil tests every year that included pH, available nutrients, and both micro and macronutrients (i.e., “Of course, pH levels, nutrient levels, macros, and micros”). He indicated using soil tests as rough guidelines mainly to address productivity issues and tissue tests to address plant nutrient needs:

“We find that what we are presented with on the soil test, the availability of nutrients isn’t necessarily the nutrients that are available to the crop we are growing”.

(Farm C’s owner/manager)

“That goes again to what I said about the generalization of just using the soil test as a rough guideline. Our soil test comes back every year, and we have potassium and calcium available, but when we start taking tissue samples when we’re growing the crop, it’s just not been enough for the plant”.

(Farm C’s owner/manager)

3.4. Land Ownership and Considerations for Land Leases

The manager of Farm A indicated that they rent about 38 percent of the land they farm and own 62 percent of the land. Farm B owns all farmland under vegetable production. Finally, the owner of Farm C indicated that they rented about 30 percent of the land they farmed and owned the remaining 70 percent (Table 1).

In order to gain insight into the farmers’ views on soil health practices, we asked farmers to indicate the conditions imposed on them in terms of practices they can use on the land they are currently renting from a landowner. We also asked a hypothetical question regarding the conditions they would impose on a tenant leasing their land, specifically related to production practices they could or could not use. They first discussed the current conditions imposed on them by the landowner on the land they rent.

The manager of Farm A indicated that no specific conditions were imposed on the land they are currently leasing from a landowner. He indicated that if they rented the land they owned to a tenant, they would probably ask the tenant to plant cover crops when fields are not in production, specifically to avoid erosion and put microbes back into the soil:

“The only thing I would impose is that they should plant cover crops after they stop producing every single year. It could be wheat, winter wheat or grass, or anything that would retain the soil (reduce erosion) and something that puts microbes back in the soil”.

(Farm A’s manager)

The owner of Farm B indicated that no conditions are imposed on the land he is renting from a landowner. Regarding the conditions he would impose if he were to rent his land to a tenant, he mentioned contour farming, especially if they were laying plastic, the removal of 100 percent of plastic mulch after the production season, with a grace period for removal of about 60 days, and finally addressing water flow issues:

“…If they want to lay plastic, it would have to be contoured, not on the up and down”.

(Farm B’s owner/manager)

“100% removal (of plastic) …some kind of deal where they had a period after the crop was done to get it (the plastic) up, like maybe a 60-day grace period…”

(Farm B’s owner/manager)

“…we would have the understanding that if there were any leaks or any major water flow issues that, they would be addressed…”

(Farm B’s owner/manager)

Farm C’s owner indicated that the current conditions imposed on the land they lease from a landowner are very loose and mostly related to keeping the field clean, specifically not dumping trash. If he were to lease his land to a tenant, he would ask tenants to conduct soil tests on a yearly basis and maintain consistent nutrient levels so that they could farm the land once the lease expires:

“I would require that they would take yearly soil tests and that they would manage the land to keep the nutrients in the soil at a level that could be used for production if the lease was expiring”.

(Farm C’s owner/manager)

He also mentioned restricting pesticide use, specifically the use of chemicals that would prevent them from using the land right after the lease ended due to pesticide rotational restrictions or the time from a particular pesticide application to the planting of a subsequent crop:

“Also, what kind of pesticides that they would use? So, there wouldn’t be any long-term effects or plant back restrictions, if we were to need to use that property”.

(Farm C’s owner/manager)

3.5. Field History and Management Practices

Farm A’s manager indicated that the “not good” field has a history of Phytophthora blight that has had a negative impact on productivity. In this field, the farm has lost about 70% of the total production in the past few years due mainly to disease pressure, which led to the decision to stop production in this field. It had been fallow for 2 years when we sampled in 2023. The “good field” had been in tomato and pepper production. This field’s yield has fluctuated due to weather and other factors, but overall, this field has maintained productivity over time. In 2023, they stopped production to let the field rest. A common practice they use on this farm is to let fields rest every three years for one year. Both fields are managed with deep tillage that is between 18 and 23 cm. The manager of Farm A indicated the use of cover crops to prevent erosion and incorporate organic matter into the fields. He mentioned winter wheat as the cover crop they use during the winter after they complete vegetable production.

The owner of Farm B indicated that the “not good” field had a history of low productivity, microbial activity, and organic matter. The “good” field had high productivity, microbial activity, and organic matter. Both fields were located in the same area and had the same cropping history. Crop rotation is a practice used on the farm; for these fields, cucurbits were produced for two consecutive years before producing tomatoes, and in 2023, these fields were used for soybean production. It was difficult for Farm B’s owner to talk about changes in yield in both fields because, in 10 years, challenges faced by different crops and varieties have changed, starting with disease pressure:

“Is that over a 10-year window? … So, ten years ago, nobody knew what bacterial leaf spot was, and so ten years ago, I was heavy in peppers, so we had no bacteria issues…. I had some varieties that I was growing ten years ago, that would out yield the varieties that I grow now… but that is the variable is the variety and the disease package that it has. If you excluded disease and varietal differences, I’m going to say we are pretty similar (to what we were ten years ago)”.

(Farm B’s owner/manager)

Overall, if the changes in disease pressure were excluded, he believed the yields of both the “good” and “not good” fields have remained consistent over time. The fields are managed with low tillage (between 2.5 and 18 cm).

The owner of Farm C indicated that for the “not good” field, they could only obtain two or three years of production before having to rotate it to a different crop because of productivity issues. He indicated they have a southern bacterial wilt issue in this field and unique weather conditions in this location (i.e., humidity and heat) that negatively impact productivity. This field was in tomato production in 2023, but in 2021 and 2022, it was in corn production. In contrast, the “good” field has been in tomato production for at least the past seven years, maintaining consistently high productivity over time. There is a difference of about 27% in tomato yield per hectare between the “good” and “not good” fields. Both fields are managed with deep tillage, using a chisel plow at a depth of at least 30 cm every other year. Just like the other farms, cover crops and crop rotation are practices used on this farm.

3.6. Nutrient Management

We asked for fertilizer application records, but none of the interview participants provided this information. The standard soil test recommendation for fertilizer application for plasticulture tomatoes in the Southeast is 146–235 kg/hectare of nitrogen, with 56 kg/hectare incorporated into the bed before mulch laying and the remaining 90–179 kg applied via fertigation weekly throughout the growing season. Phosphorous and potassium are recommended to be applied according to soil test recommendations. More growers are now combining plant tissue analysis and soil tests to inform fertilizer recommendations (https://tiny.utk.edu/ywagn, https://tiny.utk.edu/CV8IB, accessed on 20 December 2024 ).

According to the manager of Farm A, they used liquid mixed fertilizer providing potassium, calcium, phosphorus, and nitrogen. Fertilizer application was adjusted constantly (i.e., every two weeks) according to tissue tests, and therefore, it is difficult to assess whether fertilizer use has increased or decreased over time.

When talking about nutrient management, the owner of Farm B talked about maintaining nutrient levels over time. Nonetheless, he mentioned that they had decreased the application of liquid phosphorous (P) and potassium (K) but have compensated for that decreased application with the application of potassium chloride, commonly known as muriate of potash, ammonium sulfate, and diammonium phosphate:

“If you want to get crop-specific, the only thing that probably has changed is tomatoes and pepper. We do not do as much liquid P and K or water-soluble P and K as we did, but we make up for that on the front end with muriate, sulfate, and DAP”.

He wanted to ensure nutrient levels were high enough not to become a limiting factor and to reduce the risk of losing a crop, especially a high-value crop. In a way, fertilizer and nutrients were seen as tools to manage yield risk:

“…on a high-value crop it is completely different than on corn or soybeans. So, I spare no expense when it comes to nutrients”.

(Farm B’s owner/manager)

“I could lose one box of tomatoes that paid for a whole lot of P and K or a whole lot of N”.

(Farm B’s owner/manager)

“…because I don’t want those fluctuations in my P, N and K levels because when I do a soil test, it’s not going to be very accurate when I have those high fluctuations. You know, when I put a bunch of phosphorus out there, that phosphorus is not available right then; it takes just a minute, and I don’t want my plant to experience that. I want my levels to stay very high the whole way through”.

(Farm B’s owner/manager)

Regarding fertilizer application and nutrient management, the owner of Farm C indicated that fertilization rates were very similar across all fields, and fertilizer application might be adjusted based on tissue test results. He believed that nutrient needs had not changed drastically, specifically for nitrogen. Nonetheless, pH has had to be adjusted over time, and the application of potassium and calcium has increased over time. He reported that although soil tests have indicated no changes in potassium, phosphorous, and calcium input needs, they increased the application rates associated with these nutrients based on tissue tests. They used soil tests as a rough guideline, but tissue tests dictated their fertilizer and nutrient needs:

“That goes again to what I said about the generalization of just using the soil test as a rough guideline. Our soil test comes back every year that we have potassium and calcium available, but when we start taking tissue samples when we’re growing the crop, it’s just not been enough for the plant”.

(Farm C’s owner/manager)

3.7. Production and Management Practices to Improve Soil Health

Farm A’s manager indicated that since he became the manager of this farm, production and management practices have not changed drastically. He believed the adoption of cover crops was a decision made about 30 years ago, and it has not changed, given the firm belief that this practice reduces erosion and increases the levels of organic matter in the soil:

“That decision (the decision to use cover crops) was made probably 30 years ago by the previous owner of the farm”.

(Farm A’s manager)

“…I think cover crops are really good stuff because they help retain the soil; when we incorporate them into their soil, they add organic material”.

(Farm A’s manager)

“I have been using winter wheat every year. When we let the fields rest, in the winter, we plant winter wheat, and the next year, we let grass grow”.

(Farm A’s manager)

Farm B’s owner indicated that as a commercial farm, decisions are rarely made based on soil health but rather profitability, knowing that the two are highly correlated:

“… I don’t base any of my decisions on soil health. It’s, I mean, we’re a commercial farm, so my decisions are based on profitability”.

(Farm B’s owner/manager)

“So, I think, health and profitability run hand in hand…”.

(Farm B’s owner/manager)

Production practices have changed over the past 30 years, mainly due to different crops being grown on the farm, changes in scale, and access to technology. He believes that there are some changes in production practices that have benefited and others that have deteriorated soil health. Sometimes, changes were driven by changes in scale. For example, erosion might have increased due to the adoption of equipment that can efficiently complete tasks on a larger scale. In contrast, the soil water-holding capacity might have increased because they stopped using equipment that had a negative impact on this characteristic due to new technologies being available on the market:

“As we have changed production practices throughout the years, I can tell you certain parts of my soil health program have deteriorated, certain parts have probably benefited. From a physical standpoint, I deal with a whole lot more erosion now because my equipment won’t operate in the two- and three-acre (5 and 7.5-hectare) fields that we did. From a physical standpoint as well, though, we don’t use the moldboard plow, so I can tell you that as far as pore capacity and water holding ability, my soil is probably better than it was when my grandfather was farming”.

(Farm B’s owner/manager)

“… you know some things we do better, and some things we do not do better, but with scale, it has changed”.

(Farm B’s owner/manager)

Farm C’s owner indicated they had used manure on the “not good” field to improve soil health, which explains the elevated levels of organic matter and active carbon measured in this field (Table 2). On all fields, they use cover crops, specifically small grains. As indicated by Farm B’s owner, profitability drives their decision-making process in terms of management practices. For example, for fields that have decent but not great production levels, the cover crop is incorporated into the soil. For high-producing fields, sometimes the cover crop is only partially incorporated back into the soil, and the rest is sold as straw. They try to maximize profits from the “good” producing fields:

“…If it (the field) is not producing well, but it is still producing enough to where we want to, then we will try to incorporate the entire growth of the cover crop and use that flail mower to put it back in, you know, and use the green manure type of additive to the soil. Anything that is just clicking along like clockwork, we will try to make money and sell straw”.

(Farm C’s owner/manager)

3.8. Second Visit: Reactions to Soil Test Results

Soil samples were taken from the fields the farmers identified as “good” or “not good” in terms of soil health and sent to the Cornell Soil Health Lab for CASH analyses. A second visit to each farm was conducted to present the results of the CASH soil tests to interview participants (Table 2).

We first explained the CASH tests to the farmers before starting to discuss the results, specifically those that the farmer may have been less familiar with, especially aggregate stability, active carbon, and organic matter. We asked farmers whether the results were consistent with what they expected in terms of soil health for the “good” and “not good” fields. We also allowed farmers to ask questions related to the soil test results.

Farm A’s manager was, in general, not surprised about the soil test results. During the first visit, it was hard for him to identify a “good” and “not good” field in terms of soil health. He stated that all fields have similar soil in terms of soil health. Therefore, the “not good” field was selected more based on soilborne disease pressure. The manager of Farm A was curious about the codification of results from the CASH test, which gives each measurement a rating from 0 to 100, defining ratings <40 as “low” or “very low” and color coding them red. We explained that the guidelines for the CASH test are developed based on soils in the US Northeast region, which has much higher levels of organic matter compared to soils in the US Southeast region. We explained that even though the CASH test flagged their soil as having low levels of organic matter, the levels (1.2 and 2.5%) were comparable to other agricultural soils in the area. We noted that the organic matter and aggregate stability were higher for his “not good” field (2.5%), likely due to the fact that it had not been in production for the last two years. He was very interested in understanding the impact of letting fields rest from production every couple of years, which is a practice they have been using on the farm for a few years. Interestingly, the manager was less interested in results related to the soils’ available nutrients, stating that plant tissue tests are the ones dictating their decisions in terms of nutrient management rather than soil fertility tests.

Farm B’s owner was pleasantly surprised about the organic matter levels in both the “good” and “not good” fields (i.e., 1.7 to 2.6%), which he felt were good. Although the slope of the “not good” field or area explains the erosion level he used in the first place to identify this field as a “not good” field, he was encouraged by the soil health test results confirming to him that his efforts to address erosion in this area have paid off. He explained that the location of his fields and the production practices he uses are related to field productivity and the logistics of running specific equipment (e.g., a plastic layer). The decisions of where and how to farm are related to efficiently using resources, knowing that these practices could negatively impact soil health. He uses specific practices (e.g., low tillage) to address the potential negative impacts of certain practices on soil health. As he mentioned during the first visit, decisions are made based on profitability, with the understanding that soil health is correlated with farm profitability. He believes that although soil health and profitability go hand in hand, many farmers might not have knowledge related to soil health and cannot use that knowledge to improve productivity and, therefore, profitability. He specifically gave an example of deep plowing as a practice that is still used by some farmers in the area, even though it is detrimental to soil health:

“So I think, health and profitability run hand in hand, but I think a lot of folks don’t have the base knowledge of (soil) health to improve their production….extreme tillage, year after year after year and they thought they were doing the right thing… we did all the things that you should have done if this was 1970s or 80s…I have always been disturbed by flipping, by taking your topsoil and rolling it. We have always done deep plowing, you know, we would plow out probably 10 to 12 inches when I was a kid…Once you fix that, that fixes a whole lot of issues. But a lot of these guys (large vegetable growers), they don’t have that understanding. They’re still farming like it’s 1970 or 80…”.

(Farm B’s owner/manager)

For Farm C’s owner, test results were generally in line with what he expected from the fields, except for the organic matter levels of the field he labeled as “good” in terms of soil health. He thought that organic matter levels (0.9%) were lower than what he was expecting. This is a field that has been in continuous tomato production for at least seven years because of stable and continuous high productivity levels. When asked about what he would consider doing differently in this field, he talked about trying a different cover crop (e.g., African cabbage, radish) than the one they were currently using (rye). Farm C’s owner had an explanation for all results related to the chemical characteristics of both fields, specifically pH, macro-, and micronutrients. He was able to connect micronutrient levels to production practices. For example, tomatoes take up relatively large amounts of calcium, resulting in lower calcium concentrations in the soil, and the application of copper-containing fungicides to control foliar diseases resulted in higher copper concentrations in the soil (Table 2).

Overall, all interview participants saw the value of the soil tests. Primarily, it helped them confirm that the practices they have implemented have had a positive impact on soil health, even though they adopted these practices with profitability goals in mind. This information might reinforce some of their beliefs and encourage them to continue the utilization of these practices.

4. Discussion

Using information from semi-structured interviews conducted with three large-scale vegetable farmers in Tennessee, we explored some insights into their perceptions of soil health and how those perceptions connect with their production decision-making processes. Furthermore, we explored how these farmers’ perceptions aligned with the results of soil health assessments.

Our study focused on large-scale conventional farming, while the previous study evaluating vegetable farmers’ perceptions of soil health focused on small-scale organic farms [17]. Like the organic farmers included in [17], we found that the farmers included in our study focused on crop health but through the lens of marketable yield and lack of soilborne diseases as indicators of soil health. The farmers in the current study also managed fertility intensively and used soil fertility as an indicator of soil health, so that nutrients were not yield limiting. In contrast, the organic vegetable farmers in [17] relied on other queues, such as soil structure, growth habits of weeds, and soil biology as indicators of soil health.

Similar to [4], results from our farmer interviews suggested that when identifying a “good” and “not good” field in terms of soil health, farmers’ perceptions provide a broader perspective that includes productivity and soilborne disease pressure. Additionally, some of the metrics farmers consider when assessing soil health (e.g., yield) do not capture soil processes and long-term soil dynamics, which is a limitation of the knowledge farmers are using to assess soil health. Interestingly, when it comes to short-term yield losses, none of the farmers cited soil health management practices as a contributing factor. Instead, other factors, such as disease, weather, or different crop varieties, were identified as the main causes of yield fluctuations. The disconnect between soil health management practices and productivity is similar to the one found by [2] when evaluating row crop farmers’ perceptions of soil health.

In terms of how farmers make decisions related to the adoption of conservation practices that could have a positive impact on soil health, it is not surprising to find that the farmers we interviewed make decisions based on profitability and not soil health. Nonetheless, Farm B’s owner explicitly recognized that there is a correlation between soil health and profitability. Additionally, although there is a tendency to try to oversimplify farmer decision-making processes to develop strategies aiming to increase farmers’ adoption of conservation practices, in reality, farmers make decisions taking into consideration various factors. Farm C’s owner defined decision-making processes in vegetable production as staying ahead of any factor that could limit productivity (e.g., water, fertility, diseases). It should be noted that the farmers included in this study use basic soil fertility tests to adjust soil chemistry but do not regularly assess soil health indicators. Indeed, except for Farm B’s owner, the farmers seem more concerned with productivity and soil disease pressure as proxies of soil health than actual soil health indicators.

Similar to previous studies [11], the farms included in this study found value in the information provided by the CASH soil tests. The owner of Farm C indicated that the information provided by the CASH soil test was valuable to assess soil health and indicated a willingness to pay for this information. Farm B’s owner was excited about using the CASH soil test information to communicate with the local Natural Resource Conservation Service (NRCS) office regarding support for production practices he wants to implement on his farm. These findings are in line with the results presented by [3,11,31], suggesting that farmers’ lack of use of soil health tests is not due to a lack of interest but due to other barriers such as availability and cost. In the Southern region of the US, the dearth of available soil health tests that present helpful information unique to this region’s soil characteristics could explain the lack of use of these tests to guide production management decisions. Nonetheless, just like the findings in [11], the manager of Farm A, although interested in the CASH soil test results, was uncertain about the value of the information and how to interpret it. Making soil tests available at a reasonable cost might not be the answer to increasing farmers’ willingness to use soil health information to make production decisions; rather, it is necessary to connect this information to practical applications to improve soil health [11]. Specifically, given that farmers have profitability goals in mind when implementing production and management practices, it is important to connect soil health test information with the economic implications (e.g., costs, revenue) associated with the adoption of these practices to assess the value of this information [10,31].

Scientific data from soil health assessments can complement farmers’ knowledge and assessment of soil health by confirming that the use of certain practices has contributed to soil health or reassessing their beliefs about the soil health impacts of using specific practices [9]. For example, Farm C’s owner was surprised about the organic matter levels in the field he considered to be a “good” field, and, therefore, considered re-evaluating the type of cover crops used in this field.

While the information presented in this study may not be scalable to all large-scale vegetable farms in the Southeast region of the US, we believe that the results from these in-depth semi-structured interviews may play an important role in translating theoretical aspects of soil health knowledge into practice. This study provides an exploratory approach using information from interviews with three large-scale operations as a starting point for documenting the important role farmer knowledge and perceptions play in better understanding the connection between soil health and farmers’ adoption of best soil management practices. Specifically, the results presented in this study will contribute to the design of future studies aiming to investigate the relationship between farmer perceptions of soil health and the adoption of best soil management practices among large-scale vegetable farmers.

One major limitation of this study is the number of farms included (i.e., three). Future studies could use the approach presented in this study to conduct interviews with farmers or managers operating large-scale vegetable farms in other states in the US Southeast region. Although there will also be limitations related to the scalability of the results from these studies, a comparison of results across states could be helpful to validate the approach and results presented in this study.

Although our study did not specifically focus on the use of soil management practices among large-scale vegetable operations, it is important to note that there is a gap in information related to the use of conservation practices and soil management practices among these farms. For example, previous studies focusing on farmers’ perceptions of soil health and farmers’ use of soil management practices mentioned tillage (e.g., no-till) as a practice farmers modify to improve soil health [2,17]. Tillage was not the focus of farmers’ conversations in this study. This is not surprising given that tillage, whether deep or low, is a practice commonly used when producing vegetable crops on a large scale. Also, findings presented in [17] suggest that small-scale organic vegetable farms included in this study use the choice of equipment as a way to manage soil health. Some farmers included in [17] mentioned the use of light tools or machinery to manage soil health. Nonetheless, as suggested by the owner of Farm C, the choice of equipment in large-scale vegetable operations has to do with scale, and sometimes, it is not an option to change the type of equipment used to manage soil health. We believe that there is value in further investigating the use of soil management practices among large-scale vegetable farmers in the Southeast region of the US, given that these data do not exist, and it could guide future programs and policies trying to increase the sustainability of large-scale vegetable production in this region.

Author Contributions

Conceptualization, M.V., A.L.W., J.D., and A.W.S.; methodology, M.V., A.L.W., and J.D.; software, M.V.; validation, M.V., A.L.W., and J.D.; formal analysis, M.V.; writing—original draft preparation, M.V.; writing—review and editing A.L.W., J.D., and A.W.S.; funding acquisition, M.V., A.L.W., and J.D. All authors have read and agreed to the published version of the manuscript.

Institutional Review Board Statement

The study was conducted in accordance with the Declaration of Helsinki, and approved by the University of Tennessee Institutional Review Board (IRB) (UTK IRB-22-07049-XM).

Informed Consent Statement

Informed consent was obtained from all subjects involved in the study.

Data Availability Statement

Data are available on request due to restrictions; given that only three farmers are participating in this study and that the population of large-scale vegetable farms in Tennessee is small, we will not give access to raw data to avoid the potential of those farmers participating in the study being identified.

Acknowledgments

We thank Doug G. Hays for his leadership in acquiring funds and overseeing the research project that supports the research presented in this article. We want to thank the farmers who agreed to participate in this study.

Conflicts of Interest

The authors declare no conflicts of interest.

Footnotes

Disclaimer/Publisher’s Note: The statements, opinions and data contained in all publications are solely those of the individual author(s) and contributor(s) and not of MDPI and/or the editor(s). MDPI and/or the editor(s) disclaim responsibility for any injury to people or property resulting from any ideas, methods, instructions or products referred to in the content.

Figures and Tables

Figure 1. The image on the left is of a tractor pulling a plastic mulch layer that is laying drip tape and plastic mulch. The image on the right is of tomato transplants on raised beds covered with black plastic mulch. Pictures were taken on Tennessee farms by Annette Wszelaki.

Figure 2. Word frequency clouds for information related to the question: “What information and soil characteristics do you use to identify your “good” and “not good” fields regarding soil health?”.

Table 1

Farmer and farm business characteristics.

	Farm A	Farm B	Farm C
Age (years)	37	39	61
Years Involved in Farming as a Farm Owner, Manager, or Primary Decision-Maker (years)	10–12	23	43
Farm Size (hectares)	263 hectares in vegetable production	49 hectares in vegetable production, 73 hectares in row crops	194 hectares in vegetable production, 32 hectares in row crops, 100 heads (livestock)
Land Ownership	62% of vegetable hectares are owned	100% of vegetable hectares are owned, 33% of the hectares in row crop production are owned	70% of the vegetable hectares are owned, 100% of the hectares in row crop production are owned
2022 Percentage of Taxable Household Income from Farming Activities	More than 75%	More than 75%	More than 75%

Table 2

Comprehensive Assessment of Soil Health (CASH) soil tests results.

Farm	A		B		C
Sample Date	9 September 2023		26 July 2023		1 December 2023
Field	“Good”	“Not Good”	“Good”	“Not Good”	“Good”	“Not Good”
Previous 3 yr Crops	PEP-TOM-TOM 1	TOM-Okra-NONE	SQS-TOM-SOY	SQS-TOM-SOY	TOM-TOM-TOM	COG-COG-TOM
Overall CASH score	46	56	59	64	59	59
Aggregate Stability (%)	2.8	15.9	14.1	24	22.1	9.4
Organic Matter (%)	1.2	2.5	1.7	2.6	0.9	3.1
Active Carbon (ppm)	231	300	277	384	131	355
Soil pH (ppm)	7.1	6.0	6.2	6.8	6.4	7.3
P (ppm)	31.4	6.1	34.8	27.6	35.3	24.1
K (ppm)	203.8	248.4	299.4	212.4	174.7	230.3
Ca (ppm)	813.7	726.6	867	1133	557.2	2229.6
Mg (ppm)	146	77	199.9	262.2	84.6	438.9
S (ppm)	2.4	18.1	6.1	7.6	27.2	58.6
Al (ppm)	19.4	110.7	15.2	11.1	17.7	8.8
B (ppm)	0.3	0.26	0.2	0.3	0.15	0.82
Cu (ppm)	NR	NR	0.3	0.2	4.63	1.15
Fe (ppm)	1	5.9	0.6	0.8	1.1	2.5
Mn (ppm)	3.2	7.5	12.6	13.9	4.9	9.9
Zn (ppm)	1.5	1	2.2	2.3	4	1.3

¹ PEP = peppers; TOM = tomatoes; SQS = summer squash; SOY = soybean; COG = corn grain.

Appendix A

First Farm Visit

Soil health and history of fields questions

• What information and soil characteristics do you use to identify your “good” and “not good” fields regarding soil health?

• What type of information do you obtain from soil tests in these fields? How do you use this information related to the management of your fields? How long have you been conducting soil tests? Based on your soil health assessment, describe whether the soil health of these fields has improved or deteriorated over time. Please walk us through how you have made those assessments. If soil test information is available, we will ask the grower to share this information with us.

Land ownership

• Please describe the ownership of the land where the selected fields are located (are fields on owned or rented land?). Has the ownership of the land where selected fields are located changed over time? How? When? Why?

• If you are renting the land that you are farming, could you please describe the conditions of your farm leases in general terms (e.g., term, cost). Are there any conditions related to production/management practices you can or cannot implement on the land you are farming?

• If you own your land and if you were to rent your land, would you impose certain conditions related to the land? If so, what production practices and soil health conditions would you impose on your tenant? And why would you impose those conditions?

• If you own the land, is there a succession plan in place? If yes, please describe the general guidelines of this succession plan. If there is no succession plan in place, please describe your future plans for the land you own and are currently farming.

History and management strategies

• Please tell us the history of the “good” and “not good” fields you selected in terms of crops grown and production practices (e.g., irrigation, plastic use, tillage, crop rotation) used. If possible, talk about the history of these fields for the past few years, including whether plastic mulch has been used continuously in these fields.

• We will ask farmers to provide yield information from these fields if that information is available. We will still ask them questions related to their perceptions about yield change over time (increased, decreased, stayed the same; we could ask this question relative to average farm yields). We will ask farmers to talk about their assessment of what factors they believe have impacted changes in yields in the “good” and “not good” fields.

• Fertilizer and nutrient management—Discuss changes in fertilizer use over time, addition of cover crops for nutrient management. Do you have records of fertilizer use on the selected fields? Would you be willing to share those records with us? If they do not have records, we will ask them about their perceptions related to changes in fertilizer use overtime. On average, has fertilizer use increased, decreased or stayed the same over the past few years?

• Have you made management decisions to improve your soil health in the selected fields? Please describe the management decisions you have made and how you believe they have improved your soil health. Walk us through the decision-making process of adopting new management practices (e.g., what motivated you to adopt the practices? What yield or input information did you use to make the decisions? What information did you gather before making that decision? Where did you get that information?).

Plastic mulch use

• For plastic use, how many years have you been using plastic mulch on your “good” field? How many years have you been using plastic mulch on your “not good” field? Please describe the plastic mulch you traditionally use on your “good” and “not good” fields (e.g., color, thickness). Have you changed the plastic mulch you use on your fields over time? How? Why? Are you satisfied with the production results with plastic mulch in your “good” and “not good” fields? Why?

• Please describe your plastic removal and disposal practices in your “good” and “not good” fields, if they are different; if they are the same, just describe removal and disposal practices in general (How do you remove it? How many people are involved in plastic removal? Do you use paid farmworkers to remove it, or do you do it yourself with the help of unpaid labor (e.g., family)? How much time does it take to remove plastic mulch in one acre or any other production unit you feel comfortable estimating this number? Do you retrieve plastic mulch fragments after removal? Why do you or don’t you remove plastic mulch fragments? How do you dispose of your plastic mulch? Is there a cost for disposing of your plastic mulch? How much do you pay for disposal (e.g., landfill tipping fees, transportation)? Have those practices changed over time? How and why?).

Stress events and field resiliency

• Please describe the major challenges you have had in those fields (e.g., “good” and “not good” fields) over time, and if you perceive these fields to have been more or less resilient or to have been able to recover faster/slower from pest, disease, climate pressure or any other events that could have caused stress in your production system.

Water use and water sources

• Please tell us about your water sources for irrigation (e.g., above-ground/surface water sources, such as rivers, streams, and ponds, or municipal water, or groundwater sources, such as wells) and water management practices. Please discuss changes in your water use over time in the “good” and “not good” fields. On average, has water use increased, decreased, or stayed the same over time?

• Have your water management practices changed over time? Why? How?

Labor use and labor challenges

• Please discuss changes in labor availability and use over time. Please discuss changes in labor use associated with crops grown on plastic mulch. Are there any differences between labor use in the “good” and “not good” fields?

Second Farm Visit

Follow-up farmer interviews

• Soil test results are returned to farmers, and a follow-up interview is conducted. This interview will explore farmers’ reactions to the soil test results and will give farmers the opportunity to ask questions.

We will ask the following questions separately for the “good” and “not good” fields’ soil test results:

• Are your perceptions of soil health related to this field in alignment with the soil test results?

• Were there any surprises? Please explain.

• Will you change your soil management practices based on these results? What practices and why?

• We will discuss the soil test results in detail and ask about their understanding of the results. We will let the farmers ask as many questions as possible about the soil test results.

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